The Preparation And Mechanical Properties Of Polyethylene Glycol Sliding Gel

Hydrogel is a kind of polymer network which is swollen in water and insoluble in water.It has excellent performance in biological,pharmaceutical,water absorbent.Traditional hydrogels are so weak in mechanical properties that severely limited their applications.People have developed a lot of novel structures to enhance the mechanical properties of the gel,in which the sliding gel has become a hotspot in recent years.Sliding gel has pulley effect because of its internal special figure-of-eight structure,the pulley effect can be a good dispersion of external force,so that the gel achieve the purpose of enhancing the mechanical properties of the gel.In order to enhance the mechanical properties of the gel,the PEG Sliding gel was successfully synthesized and the mechanical properties of the gel were promoted.The details are as follows:(1)The hydroxyl groups at both ends of the PEG chain were oxidized to carboxyl groups by oxidation reaction with TEMPO,sodium hypochlorite and sodium bromide as the oxidation system to obtain HOOC-PEG-COOH,which yied is 82%.The structures were characterized by 1H-NMR,IR and TGA.(2)The method of ultrasonic is used to promote the threading and complexation between HOOC-PEG-COOH chain and a-CD,and the pseudorotaxane product was washing by centrifugation at low temperature to inhibit the disassembly.The complexation degree of pseudorotaxane was calculated by using the peak area of 1H-NMR spectral.At the same time,The effects of the mass ratio of HOOC-PEG-COOH and α-CD,reactinon time and temperature on the yield and complexation degree of pseudorotaxane were investigated.So the optimum conditions for the synthesis of pseudorotaxane were as follows:the mass tatio of HOOC-PEG-COOH and α-CD was 1:15,the ultrasonic time was 2h after the addition ofα-CD aqueous solution,and the reactinon temperature in the range of 15 to 17℃.Under these conditions,the yield of pseudorotaxane was 46.46%,and the complexation degree reached 80.70%.The structures were characterized by 1H-NMR,IR and TGA.(3)With amantadine as the capping agent,BOP and DIPEA as the catalytic system,the PEG pseudorotaxane capped to obtain polyrotaxane.The effects of the mass ratio of amantadine and pseudorotaxane,DIPEA and BOP,reactinon time and temperature on the yield of polyrotaxane were investigated.The optimum conditions for preparing polyrotaxane were as follows:the mass ratio of amantadine and pseudorotaxane was 1:32,the mass ratio of DIPEA and BOP was 1:1.6,the reaction time was 24h,and the reaction temperature was 4℃.Under these conditions,the yield of polyrotaxane was 40.66%,and the complexation degree reached 40.35%.The structures were characterized by 1H-NMR.(4)With hexamethylene diisocyanate as the crosslinking agent,the polyrotaxane crosslinked to get sliding gel.The crosslinking density had a significant effect on the strength of the hydrogel.The maximum compressive stress of the gel was 11.64MPa,and the tensile stress was 0.42MPa.